Filter for 5 1/2 gallon tank

Question
I recently obtained a Whisper ex 10 (5-10 gallons) and have it hanging on the outside of my betta's 5 1/2 gallon tank. The package for this filter says it filters 90gph. It is not adjustable either. What I am wondering is if this is too much for my betta, i.e. the current it too strong. I cannot tell if he is ok with it, or if it is stressing him out. Do you know what gph is recommended for a betta in this size tank? I was considering a Duetto Multi Filter 50, as it is adjustable and only goes up to 55gph. I would hate to come home and find out my betta has decided to give up on swimming and is sitting stuck to the intake pipe of the filter. I have heard that air pump operated filters are gentler for bettas, but the one I had had to be changed too often, as it was so small.

Thank you for your time.

Answer
Hello,
Betta's do not like strong current, if he is fighting a current, it could stress him, and then you end up with disease.  The Duetto Multi Filter 50, would be a better choice.  Even though you have a filter, you must do water changes weekly, so that you don't have ammonia build up.  Ammonia is the biggest killer of fish.  The Betta is very sensitive to this, so make your water changes every week, and add a teaspoon of aquarium salt to your water.  There are different sizes of air pumps...maybe a corner one would do just fine.  Remember, no matter what filter you use, you will have to rinse it and clean your aquarium every week. I just want to add, that when you clean your filter materiel, rinse it the same temperature as your aquarium water... this is very important as to not kill your good bacteria.
Hope this helps
Lynda